Valves are known to be useful for regulating the flow of fluids. Moreover, compressible and expandable bellows structures have been known to be useful for controlling pressurized fluids to better regulate such valves. In the context of high pressure applications, bellows can be used to control the opening and closing of valves to regulate the flow of fluids through valves, while minimizing the risk of valve failure. However, bellows themselves can also be subject to failure in high pressure conditions.
A standard edge-welded bellows having spherical welds is typically comprised of metal plates welded together, where the thickness of the plates often measures between one and twenty thousandths of an inch. More often, the thickness of such plates is typically between three and five thousandths of an inch. Such standard edge-welded bellows can typically last up to a minimum of 10,000 cycles at a relatively low pressure of 100 pounds per square inch (psi). At higher pressures registering in thousands of psi, such standard edge-welded bellows can fracture, as a result of fatigue or high stress, so as to render them incapable of reaching such cycle objectives.
There is also a tradeoff between the thickness of a bellow's plates and the stress caused by that bellow's deflection. The bending stress of a bellow's deflection can be decreased by reducing the thickness of the bellow's plates. On the other hand, the plates must be thick enough to withstand the pressure differential across the bellows. High differential pressures across the surfaces of the plates within a bellows can cause failure because edge-welded bellows plates are fairly thin, typically less than one one-hundredth of an inch in thickness.
As valve and bellows technology has improved, it has become increasingly important to create valve assemblies capable of withstanding pressures in excess of 5,000 psi. Indeed, several practical applications have arisen generating the need for valve assemblies in which very high fluid pressure is utilized to open or close the valve. For example, one type of valve assembly that must withstand increasingly high pressure are gas lift valves, which are traditionally used in oil wells to aerate crude oil, thereby decreasing the weight of such oil and easing its extraction. Standard gas lift valves are well known in the art, and have been described in detail, for example, in U.S. application Ser. No. 13/195,468, assigned to Weatherford/Lamb, Inc., published as U.S. Pat. App. Pub. No. 2013/0032226 A1 (the “'468 application”), the entirety of which is incorporated herein by reference. Various other gas lift applications, in which bellows-type valve structures are described, include U.S. Pat. No. 6,827,146, as well as U.S. application Ser. Nos. 10/393,558, 12/603,383, and 13/900,114, which were published as U.S. Pat. App. Pub. Nos. 2004/0182437 A1, 2010/0096142 A1, and 2013/0312833, respectively.
FIG. 1 of the '468 application demonstrates how gas lift valves 40 are typically housed within side pocket mandrels 30 spaced along the production string 20. ('468 application, at ¶ [0003]-[0004].) The '468 application notes that conventional gas lift valves are incapable of operating under pressures in excess of 2,000 psi, even though, as described therewithin, gas lift system operators sought systems capable of operating in pressures of up to 5,000 to 6,000 psi. ('468 application, at ¶ [0013].) The continuous extraction of oil worldwide has begun to deplete oil resources, with much of the “low hanging fruit” having already been extracted. Therefore, oil wells are now located at greater depths than ever before, and extracting that oil at such greater depths, particularly in the context of deep water offshore drilling, requires that valves be capable of withstanding enormous amounts of pressure—even greater than those stated in the '468 application.
It is believed that the ideal valve assembly for gas lift valves for current needs should be capable of withstanding up to 10,000 psi or greater, while lasting for at least 10,000 cycles. It is further believed that conventional valve assemblies have difficulty in withstanding such pressures, especially withstanding such pressures for such long life cycles.